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You're more likely to inherit Alzheimer's disease from your mother than your father, a new study suggests.

People whose mothers have Alzheimer's disease had twice as much gray matter shrinkage in certain brain regions as people whose fathers had Alzheimer's and people without a family history of the disease, according to a new study.

The finding adds to evidence that Alzheimer's is highly heritable from first-degree relatives, said study author Robyn Honea, of the University of Kansas School of Medicine.

"In people with a maternal family history of the disease, we found differences in the breakdown processes in specific areas of the brain that are also affected by Alzheimer's disease, leading to shrinkage," Honea said in a statement.

Honea and colleagues conducted brain scans and tested the mental abilities of 53 healthy people, ages 60 and older, for two years. Of the participants, 11 had a mother with Alzheimer's,10 had a father with Alzheimer's, and 32 did not have a family history of Alzheimer's, according to the study.

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The researchers found that people whose mothers had Alzheimer's disease had about one-and-a-half times more whole brain shrinkage per year than those who had a father with the disease, the study said. Shrinking of these brain regions, or brain atrophy, occurs in Alzheimer's disease.

One possible reason for the bigger influence of having a mother with the condition is that a couple's children inherit all of their mitochondria from their mother (sperm cells bring DNA and little else to the egg). The mitochondria are the energy-generating structures inside cells, and abnormalities within them may be partly responsible for the shrinking of brain regions seen in some cases of Alzheimer's, the study said.